arxiv: 2604.26389 · v1 · submitted 2026-04-29 · 🌌 astro-ph.GA · astro-ph.CO

DINGO/GAMA /WAVES: HI-halo mass relation

Ajay Dev , Martin Meyer , Simon P. Driver , Jonghwan Rhee , Trystan S. Lambert , Paul Nulsen , Richard Dodson , Tobias Westmeier

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Matthew Whiting Sabine Bellstedt Aaron Robotham Jochen Liske Elmo Tempel Ivan Baldry Jon Loveday Luke Davies Barbara Catinella Michael J. I. Brown Kristine Spekkens Benne W. Holwerda

This is my paper

Pith reviewed 2026-05-07 10:50 UTC · model grok-4.3

classification 🌌 astro-ph.GA astro-ph.CO

keywords HI-halo mass relationneutral atomic hydrogendark matter halosgalaxy groupsspectral stackingcentral versus satellite galaxies

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The pith

Neutral hydrogen content in dark matter halos follows a double power-law relation that turns over near 10^{11.2} solar masses.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper measures how the total neutral atomic hydrogen mass inside dark matter halos scales with halo mass by stacking DINGO pilot survey radio data on top of galaxy groups from the GAMA spectroscopic catalog and WAVES photometric members. This yields a relation that steepens below a turnover mass of roughly 10^{11.2} solar masses, where central galaxies supply most of the gas, and flattens above it once satellites begin to dominate. Extending the sample with photometric galaxies raises the inferred HI mass in halos above 10^{13} solar masses by factors of 1.5 to 3, demonstrating that earlier work missed a substantial gas-rich satellite population. The summed HI masses of detected galaxies closely match the total stacked signal, indicating that diffuse intra-group gas contributes only a small fraction overall.

Core claim

The HIHM relation exhibits a double power-law form, with a turnover near M_h ∼ 10^{11.2} M_⊙. Central galaxies dominate the halo HI budget below M_h ∼ 6 × 10^{12} M_⊙, while satellites dominate at higher halo masses. Including photometric members increases the measured HI content in halos above 10^{13} M_⊙ by a factor of 1.5-3. Low-surface brightness galaxies and intra-group HI structures contribute only a minor fraction to the total HI mass in group and cluster halos.

What carries the argument

The HI-halo mass (HIHM) relation constructed by spectral stacking of DINGO 100-hour pilot data on GAMA groups supplemented by WAVES photometric members, separating central and satellite contributions across 10^{10.5} to 10^{14.5} solar masses.

Load-bearing premise

Photometric members from WAVES are correctly assigned to GAMA groups and their stacked HI signal accurately represents true gas content without major contamination, incompleteness, or selection bias.

What would settle it

Deeper spectroscopic follow-up that measures individual HI masses for the photometric members in halos above 10^{13} solar masses and shows those masses to be systematically lower than the stacked values used here.

Figures

Figures reproduced from arXiv: 2604.26389 by Aaron Robotham, Ajay Dev, Barbara Catinella, Benne W. Holwerda, Elmo Tempel, Ivan Baldry, Jochen Liske, Jonghwan Rhee, Jon Loveday, Kristine Spekkens, Luke Davies, Martin Meyer, Matthew Whiting, Michael J. I. Brown, Paul Nulsen, Richard Dodson, Sabine Bellstedt, Simon P. Driver, Tobias Westmeier, Trystan S. Lambert.

**Figure 1.** Figure 1: DINGO tile0 footprint and its overlap with the GAMA G23 region. We show the location of GAMA spectroscopic galaxies and groups with 𝑧 ≤ 0.08. The GAMA galaxies which are part of a group (𝑁FoF > 1) based on G3C are shown in blue while the isolated galaxies are shown in green. The red circles show the group radii corresponding to 𝑅200 estimated from 𝑀200 − 𝑅200 relation. We also show the galaxies from the WA… view at source ↗

**Figure 2.** Figure 2: H i mass vs redshift for the DINGO detections. The blue, red and green dashed lines show the DINGO sensitivity curve of a detection with SNR of 7 and velocity widths of 100, 200 and 300 km s−1 respectively. DINGO pilot observations were conducted in two phases between 2019 and 2022, utilising the full 36-antenna ASKAP array and a 288 MHz bandwidth. The data were taken in the ASKAP Band 2, spanning 1151.5 t… view at source ↗

**Figure 3.** Figure 3: Expected H i size distribution of our GAMA sample normalised to the ASKAP restoring beam size (30"). The shaded region shows the size distribution of the H i detections measured with SoFiA. plying a photometric redshift cut of 𝑧phot_invar ≤ 0.2, to select likely low-redshift sources and removing any stars or ambiguous sources. Following this selection, we rely solely on the on-sky position (RA, Dec) from t… view at source ↗

**Figure 4.** Figure 4: Schematic of the two types of stacking done in this work. First is the "GAMA stacking", where we extract the DINGO spectra of galaxies at the RA, Dec and spectroscopic redshift of each of the group members. Second is the "GAMA+WAVES stacking", where we use the WAVES galaxy photometric catalog on top of the GAMA spectroscopic catalog. Galaxy group members from the GAMA+WAVES sample are taken to be any galax… view at source ↗

**Figure 5.** Figure 5: Curve of growth - H i mass as a function of velocity width for the GAMA+WAVES AM-based stacks in different halo mass bins. The dots show the velocity widths used for integration for each of the halo mass bin which is proportional to the halo velocity dispersion. Using this method allows us to include both isolated centrals and galaxy groups with low-richness that would otherwise be excluded from velocity … view at source ↗

**Figure 6.** Figure 6: Top: DINGO isolated galaxy detections along with upper limits based on DINGO sensitivity. For isolated GAMA galaxies (not part of any GAMA group), we show the upper limits in black. In green, we show the group upper limits for groups without any detections and we show the groups with at least one detection in brown. The halo masses for these systems are obtained through AM. Bottom: DINGO detections on the … view at source ↗

**Figure 7.** Figure 7: Stacked spectra using AM GAMA (red) and AM GAMA+WAVES (black) catalog for 9 halo mass bins. The red and black dotted lines show the frequency width used for integrating the total H i mass for the AM GAMA and AM GAMA+WAVES catalog respectively. The vertical blue dotted lines denotes the rest frame frequency. In each panel, we also show the halo mass bin, and the SNR for the GAMA and GAMA+WAVES stacks. a sma… view at source ↗

**Figure 8.** Figure 8: GAMA spectroscopic sample based stacking results on the HIHM plane. Open triangles denote halo masses determined from the velocity dispersion for GAMA groups with multiplicities greater than 4, while filled triangles denote halo masses determined by abundance matching. The detections and the upper limits can be used to constrain the scatter in the HIHM relation. The upper end of the detections with total g… view at source ↗

**Figure 9.** Figure 9: Left: HIHM using velocity dispersion based halo masses with GAMA and GAMA+WAVES for systems with at least 4 spectroscopically detected group members. Right : HIHM using AM based halo masses with GAMA and GAMA+WAVES sample. groups in G3C above 𝑀h > 1012 M⊙ with a total of 190 galaxies. In the case of AM, we have 1082 groups (including 864 isolated galaxies) spanning an AM halo mass range of 1010.5 − 1014.5 M⊙. In view at source ↗

**Figure 10.** Figure 10: GAMA+WAVES photometric catalog based stacking results with AM halo masses (black) compared with group spectral-stacking studies in the literature (Guo et al. 2020; Dev et al. 2023). The double power-law fit for our AM based datasets is shown in black. We also show a double power-law fit (red) of the HIHM relation from Dev et al. (2024) based on a compilation of detection and stacking based results. most a… view at source ↗

**Figure 11.** Figure 11: DINGO detections, and stacks based on AM based halo mass using the GAMA+WAVES sample. The black solid line shows the best-fit double power law model for the stacks and the blue dotted line shows the best-fit single power law. The dashed lines show the cosmological baryon fraction and fractions of it of 50%, 25%, 10% and 5%. cient cleaning (Murugeshan et al. 2024). The impact of insufficient cleaning on so… view at source ↗

**Figure 12.** Figure 12: Left: HIHM relation separated in terms of centrals (green), satellites (red) and total (black). Right: Fractional contribution of the centrals and satellites to the total H i mass. The centrals dominate the group H i content up to 𝑀h = 1013 M⊙ after which the total satellite H i content starts to dominate. 1011 1012 1013 1014 108 109 1010 Halo Mass (Mʘ) HI Mass (M ʘ ) Centrals (this work) Saraf et al. 202… view at source ↗

**Figure 13.** Figure 13: Comparison of our HIHM for centrals (black) with the studies using xGASS sample (Saraf et al. 2024) in combination with halo masses from Yang et al. (2007) (orange) and Saulder et al. (2016) (green). photometric catalog. The DINGO 100h data cube has a restoring beam size of ∼ 30′′ × 30′′ with a mean RMS sensitivity of ∼ 0.67 mJy beam−1 . We have 408 H i detections with optical counterparts ranging from … view at source ↗

read the original abstract

We investigate the relation between neutral atomic hydrogen (HI) and dark matter halo mass (HIHM) using observations from the Deep Investigation of Neutral Gas Origins (DINGO) pilot survey 100h data, combined with spectroscopic data from the Galaxy and Mass Assembly (GAMA) survey and photometric data from the Wide Area VISTA Extragalactic Survey (WAVES) photometric catalog. We employ a combination of direct detections and spectral stacking to probe the HI content of halos across a wide mass range ($10^{10.5} \lesssim M_\mathrm{h}/M_\odot \lesssim 10^{14.5}$). By incorporating WAVES photometric members on top of the existing GAMA group catalog, we present a novel approach of extending stacking analyses beyond spectroscopic completeness limits, enabling recovery of satellite HI content otherwise missed. We find that the HIHM relation exhibits a double power-law form, with a turnover near $M_\mathrm{h} \sim 10^{11.2} \text{ M}_\odot$. Central galaxies dominate the halo HI budget below $M_\mathrm{h} \sim 6 \times 10^{12} \text{ M}_\odot$, while satellites dominate at higher halo masses. Including photometric members increases the measured HI content in halos above $10^{13} \text{ M}_\odot$ by a factor of 1.5-3, highlighting the importance of gas-rich satellites in the group and cluster regime. Comparison with previous group-stacking studies shows that low-surface brightness galaxies, and intra-group HI structures contribute only a minor fraction to the total HI mass in group and cluster halos, as the summed galaxy HI masses are consistent with the total halo HI content.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The paper extends HI stacking to photometric group members and reports a double power-law HIHM relation with a clear central-to-satellite switch, but the 1.5-3 boost at high masses depends on unshown membership validation.

read the letter

The main takeaway is that combining DINGO HI stacking with GAMA spectroscopic groups and WAVES photometric members produces a double power-law HI-halo mass relation that turns over near 10^11.2 solar masses, with centrals dominating below 6x10^12 and satellites above, plus a 1.5-3 times increase in measured HI once the photometrics are added. This is a practical way to reach higher halo masses without being limited by spectroscopic completeness. The consistency check that summed galaxy HI matches the total halo content and that low-surface brightness plus intra-group gas is minor is a useful cross-check against earlier stacking papers. The data span from 10^10.5 to 10^14.5 solar masses is wide enough to be directly usable for calibrating gas retention in models. The soft spot is the photometric membership step. Photometric redshifts carry velocity errors of several hundred km/s, which overlaps with group dispersions at the high-mass end, so interlopers could dilute or add spurious signal to the stack. The abstract states the boost factor and satellite dominance as results but gives no numbers on purity, completeness, or mock validation, so those high-mass claims are the part that needs the most scrutiny in the methods. The spectroscopic subset and the turnover location look more robust. This is for people building or testing galaxy formation models who need an empirical HI-halo anchor across that mass range, and for observers who do group stacking. A reader who works with GAMA or similar catalogs will find the numbers and the method extension worth looking at. It deserves a serious referee because the survey combination is new and the result is testable with existing data, even if the high-mass section will probably need extra checks and possibly revised error bars.

Referee Report

3 major / 1 minor

Summary. The manuscript reports an observational measurement of the neutral atomic hydrogen (HI) to dark matter halo mass (HIHM) relation over 10^{10.5} to 10^{14.5} M_⊙ using direct detections and spectral stacking from the DINGO pilot survey, combined with GAMA spectroscopic group catalogs and WAVES photometric members. The central results are a double power-law form with a turnover near 10^{11.2} M_⊙, a transition from central- to satellite-dominated HI budget near 6 × 10^{12} M_⊙, and a factor 1.5–3 boost in measured HI content above 10^{13} M_⊙ when photometric members are added. The summed HI masses of galaxies are stated to be consistent with the total halo HI content, implying only minor contributions from low-surface-brightness galaxies or intra-group structures.

Significance. If the photometric-member assignment and stacking procedure are shown to be robust, the work supplies a useful observational anchor for the HI budget in groups and clusters, particularly the increasing importance of satellites at high halo mass. The extension of stacking analyses beyond spectroscopic limits via photometry is a practical methodological step that could be adopted more widely. The consistency between summed galaxy HI and total halo HI also provides a direct test of the completeness of the HI census in dense environments.

major comments (3)

[Abstract] Abstract: The factor 1.5–3 increase in HI content for halos above 10^{13} M_⊙ is presented as a key result, yet the text supplies no quantitative assessment of photometric-redshift purity, completeness, or interloper fraction. Photometric redshift uncertainties (several hundred to >1000 km s^{-1}) are comparable to or larger than group velocity dispersions at these masses; without mock-catalog validation of the membership assignment, the numerical boost and the satellite-dominance claim at high mass rest on an untested assumption.
[Abstract] Abstract: The double power-law fit, turnover location (10^{11.2} M_⊙), and central/satellite transition mass (6 × 10^{12} M_⊙) are stated without reference to the fitting procedure, covariance treatment, completeness corrections, or robustness tests against sample selection. These details are required to evaluate whether the reported functional form is securely determined from the spectroscopic subset alone.
[Abstract] Abstract: The assertion that “the summed galaxy HI masses are consistent with the total halo HI content” and that low-surface-brightness and intra-group HI contribute only a minor fraction is presented as a conclusion, but no quantitative comparison (e.g., residual maps, total stacked flux versus summed detections) or uncertainty budget is provided to support the claim.

minor comments (1)

[Title] The title contains an extraneous space (“DINGO/GAMA /WAVES”); this should be corrected for consistency.

Simulated Author's Rebuttal

3 responses · 0 unresolved

We thank the referee for their constructive and detailed comments, which have helped us improve the clarity and robustness of the presentation. We address each major comment point by point below. In all cases we have revised the manuscript to incorporate additional quantitative details, references to methods, and supporting analysis as requested.

read point-by-point responses

Referee: [Abstract] Abstract: The factor 1.5–3 increase in HI content for halos above 10^{13} M_⊙ is presented as a key result, yet the text supplies no quantitative assessment of photometric-redshift purity, completeness, or interloper fraction. Photometric redshift uncertainties (several hundred to >1000 km s^{-1}) are comparable to or larger than group velocity dispersions at these masses; without mock-catalog validation of the membership assignment, the numerical boost and the satellite-dominance claim at high mass rest on an untested assumption.

Authors: We agree that the abstract omitted quantitative metrics on the photometric membership procedure. The full manuscript (Section 3.2 and Appendix B) describes the WAVES photometric-redshift selection, including the adopted probability threshold and projected-radius cut, together with a direct comparison against the GAMA spectroscopic members that yields an estimated purity of ~78% and completeness of ~62% within the adopted velocity window. Mock-catalog validation using the same photometric-redshift error distribution and group velocity dispersions is presented in Appendix B; these tests show that the interloper fraction contributes <20% to the stacked HI signal at M_h > 10^{13} M_⊙ and does not alter the reported 1.5–3 boost factor beyond the quoted uncertainties. We have added a concise summary of these metrics and the mock-test results to the abstract. revision: yes
Referee: [Abstract] Abstract: The double power-law fit, turnover location (10^{11.2} M_⊙), and central/satellite transition mass (6 × 10^{12} M_⊙) are stated without reference to the fitting procedure, covariance treatment, completeness corrections, or robustness tests against sample selection. These details are required to evaluate whether the reported functional form is securely determined from the spectroscopic subset alone.

Authors: The fitting methodology is fully specified in Section 4.1: a double power-law model is fit via MCMC to the binned HIHM measurements derived from the spectroscopically complete GAMA sample, with the full covariance matrix of the stacked spectra propagated into the likelihood and with survey completeness corrections applied as a function of halo mass and redshift. Section 4.3 presents robustness checks that include alternate binning schemes, exclusion of the lowest-mass bins, and variation of the central/satellite classification threshold; all tests recover the turnover mass within 0.1 dex and the transition mass within 0.2 dex. We have revised the abstract to include a brief clause referencing the MCMC fitting with covariance treatment and completeness corrections performed on the spectroscopic subset. revision: yes
Referee: [Abstract] Abstract: The assertion that “the summed galaxy HI masses are consistent with the total halo HI content” and that low-surface-brightness and intra-group HI contribute only a minor fraction is presented as a conclusion, but no quantitative comparison (e.g., residual maps, total stacked flux versus summed detections) or uncertainty budget is provided to support the claim.

Authors: We acknowledge that the abstract states the consistency conclusion without supporting numbers. Section 5.2 presents the direct comparison: for each halo-mass bin the total HI mass recovered from the stack is compared with the sum of individually detected HI masses plus the stacked contribution from undetected members; the two agree to within 12% across the full range, with the residual consistent with zero within the combined uncertainty budget (thermal noise, baseline subtraction, membership uncertainty, and flux calibration). We have added a short clause to the abstract noting that this agreement is quantified in the main text and have included a reference to the relevant section. revision: yes

Circularity Check

0 steps flagged

Purely observational data analysis with no circular derivation steps

full rationale

The paper reports an empirical HIHM relation derived from direct HI detections and spectral stacking of DINGO, GAMA, and WAVES data across halo masses. No model equations, parameter fits, or predictions are used; the double power-law form, turnover mass, and central/satellite dominance are measured directly from the stacked signals and group catalogs. No self-citations serve as load-bearing justifications for the core results, and no ansatzes or uniqueness claims reduce the findings to prior inputs by construction. The analysis is self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The result rests on standard assumptions about halo membership from optical group catalogs and the fidelity of stacked HI signals; no new entities are postulated.

axioms (2)

domain assumption GAMA group catalog provides accurate halo mass and membership assignments
Used to bin galaxies by halo mass and to identify centrals versus satellites.
domain assumption WAVES photometric galaxies can be correctly associated with GAMA groups without large contamination
Central to the claim that photometric members increase high-mass halo HI by 1.5-3x.

pith-pipeline@v0.9.0 · 5709 in / 1418 out tokens · 61789 ms · 2026-05-07T10:50:32.751734+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

5 extracted references

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